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COMPRESSED AIR MOTOR. No. 270,982. Patented Jan.Z3, 1883.

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(No Model) 2 Sheets-Sheet O. W. POTTER.

COMPRESSED AIR MOTOR.

No. 270,982. Patented Jan.23, 1883.

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' UNITED STATES PATENT OFFICE.

CHARLES W. POTTER, QF NEW YORK, N. Y.

COMPRESSED-AIR MOTOR.

SPECIFICATION forming part of Letters Patent N0.- 270,989, dated January 23, 1883,

Application filed April 24, 1882. '(No model.) i

- by means of compressed air it is necessary for the sake of portability to magazine the air at a pressure eight or ten times as great as is required for use in'the cylinders.

Although I do not confine my invention entirely to its applicability to locomotives, yet for purposes of reference and description I will refer to it as applied to any locomotive which uses compressed air as its motive power.

I am aware that patents have been taken out for compounding the cylinders in air-motors in order to use the air at its high initial pressure, and by so doing avoid the loss (hereinafter explained) which has hitherto always occurred when the air has to be lowered to a convenient working pressure by means of a reducing-valve. This, however, entails complication, and, moreover, has not been found to achieve the desired result. I propose by my invention, which is applicable to any compressed-air engine carrying its supply of air stored at a higher pressure than the actual working pressure, to obviate this loss, at the same time using the air at any convenient working pressure which may be decided upon, and storing it originally at any higher pressure which may be necessary in order to earrya sufficient quantity in a limited space.

Before describing my apparatus I will illustrate by the diagram, Figure 1, the extent of the loss which exists in all cases where highpressure air is reduced to a lower pressure before being used. Fig. 2 is a longitudinal vertical section of the injector; and Fig. 3, a side elevation, showing my invention applied to a compressed-air motor. 7

The rectangle A B O D, Fig. 1, represents any volume of air at atmospheric pressure. In order to compress this air, say, for example,

sixty-eight times, or to a pressure of ten hundred and twenty pounds above the vacuum, an amount of power is required represented approximately by the curved line a E b. Now, suppose this volume to be reduced to a working pressure of, say, one hundred and fifteen pounds, the power developed by its expansion is represented by the curved line a E. As, however, the volume and pressure represented by the rectangle F E O H cogstitute the total efficiency of the air after its expansion, it follows that the amount of power represented by the shaded part of the diagram A F E has been lost by free expansion, and the loss is, in the particularcase I have selected for my illustration,equal to about sixty-eight per cent. of the total efficiency of the air stored. This can also be demonstrated as follows: The horsepower contained in one cubic foot of airat one thousand pounds pressure is 14.23. The horsepower contained in ten cubic feet of air at one hundred pounds pressure (though equal in volume of free air to one cubic foot at one thousand pounds) is only 4.53, showing a loss in power by free expansion from one thousand pounds of 9.7 horse-power, or 68.1 percent. ofthe total power. In other words, if a certain volume of air at acertain high pressure be applied directly' to do work upon the piston of an engine, it will develop a certain power proportional to the powerspent'in compressing it; but ifthissame volume of air be allowed to expand freely to a lower pressure before being allowed to do its work on the piston the power developed on the piston will in this case be considerably reduced-in fact, it will only be proportional to the power which would have been required to compress the air originally to this lower pressure. A loss isin'curred, therefore, directly proportional to the amount of power which was actually expended in compressing it originally from the lower pressure to the higher; and, to continue the illustration of the case, if the same volume of air be allowed to freely expand still furthersay down to atmospheric pressureit would then exert no power at all on the piston, and the whole original work of compression would be entirely lost. It will therefore easily be seen that, in all compressedair motors in which the pressure of the air before beingadmitted to the cylinders is reduced by free expansion to a lower pressure than that to which it was necessary to compress it originally in order to carry a sufficient quantity, a loss is incurred proportional to the amount of reduction, or, in other words,to the difference between the storage and the working pressures.

Having now shown the nature and extent of the loss incurred in lowering the pressure of the-air by passing it through an ordinary reducing-valve, (commonly called wire-drawing it,) I Will explain the mode by which I pro-. pose to reduce this loss to a minimum.

The principle of my invention consists in so controlling the expansion of the air from the storage to the working pressure, which now takes place uselessly, as to make it do useful and valuable work, which must evidently be a clear gain; and I accomplish this by causing the expansion of the storage air down to working pressure to take place in a suitablyconstructed injector, through which the expanding air draws along with it into the cylinder (or a second low-pressure storage-tank) an additional volume of air from the atmosphere, thus supplying to the engine a larger amount of air at working pressure than would have been supplied merely by the expansion of the storage air.

Referring to the drawings, Fig. 2, Sheet 2, is a section of my injector, in which A is a pipe leading from the high-pressure storagereservoir, and B a low-pressure chamber, into which the reduced air is discharged, and from which it is conducted to the cylinders of the motor. 0 is the discharging and D the receiving nozzle, and E the chamber, in which a vacuum is formed by the Velocity ofthe highpressure air rushing through the nozzles. F is a check-valve for the admission of atmospheric air to the chamber E.

Fig. 3, Sheet 1, shows the invention applied. A is a cylinder, and B B the wheels, of a compressed-air locomotive. O is the high-pressure and D the low-pressure reservoir. E is the injector, placed between them. F is a reducing-valve, which is operated by a loaded piston carried in a cylinder, G, so weighted as to shut the valve F when the pressure in the low-pressure chamber D shall reach any required height. H is a flange secured to the pipe 0 of the discharging-nozzle, by means of which the position of the latter can be adjusted;

but this adjustment may also be performed automatically, if convenient.

The mode of working is as follows: When the reducing-valve F is opened the high-press- .ure air from the storage-reservoir U rushes with intense velocity through the nozzles contained in the chamber E, and expands freely to any required working pressure in the lowpressure reservoir D. The great velocity of thejet ofair creates a vacuum in the chamber E, and air from the atmosphere enters through the check-valve F, Fig. 2, and is carried by the jet into the low-pressure reservoir D. It will thus be seen that while the high-pressure air is being reduced to a working pressurea constant additional supply of air is being carried with it into the low-pressure chamber, and this gain in volume of low-pressure air is due to the surplus energy of the high-pressure air,which,i-n this case, instead of being uselessly expended by free expansion, is transformed into velocity and made to perform work. The nozzles of the injector are so shaped as to give the best results, and the distance between them may be varied either automatically or by hand to suit the varying pressure in the high-pressure reser- VOlI.

What I claim as my invention, and desire to secure by Letters Patent, is-- 1.- In compressed-air motors with an airstorage of higher pressure than the initial working pressure in the cylinders, the mode described of utilizing the energy of the stored air above such initial working pressure, usually lost by free expansion, by causing this expansion to produce useful work in the shape of an additional supply of atmospheric air to the cylinders, (or low-pressure chamber,) substantially as set forth.

2. In a compressed'air motor, with an airstorage of higher pressure than the initial working pressure in the cylinders, the combination, with the high-pressure storage'reservoir, of an injector supplied therefrom and forcing-an additional amount of atmospheric air into the intermediate low-pressure chamber, which supplies the valve-chests of the Working-cylinders.

3. In an injector operating, as described above, in connection with a compressed-air motor, means for adjusting, either by hand or automatically, the relative distances ofthenozzles, thereby regulating thework of the injector in proportion to the pressure in the storage-reservoir, in combination with a checkvalve opening inward.

In witness whereof I have hereunto set my hand this 20th day of April, 1882.

CHAS. W. POTTER.

In presence of JAS. SAUNDERS, EDWARD F. PIOKENS. 

